Re: [PATCH net-next v5 04/15] net-timestamp: support SK_BPF_CB_FLAGS only in bpf_sock_ops_setsockopt

[Martin KaFai Lau <martin.lau@linux.dev>]

On 1/12/25 3:37 AM, Jason Xing wrote:
> We will allow both TCP and UDP sockets to use this helper to
> enable this feature. So let SK_BPF_CB_FLAGS pass the check:
> 1. skip is_fullsock check
> 2. skip owned by me check
> 
> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
> ---
>   net/core/filter.c | 27 +++++++++++++++++++++------
>   1 file changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 1ac996ec5e0f..0e915268db5f 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5507,12 +5507,9 @@ static int sol_ipv6_sockopt(struct sock *sk, int optname,
>   					      KERNEL_SOCKPTR(optval), *optlen);
>   }
>   
> -static int __bpf_setsockopt(struct sock *sk, int level, int optname,
> -			    char *optval, int optlen)
> +static int ___bpf_setsockopt(struct sock *sk, int level, int optname,
> +			     char *optval, int optlen)
>   {
> -	if (!sk_fullsock(sk))
> -		return -EINVAL;
> -
>   	if (level == SOL_SOCKET)
>   		return sol_socket_sockopt(sk, optname, optval, &optlen, false);
>   	else if (IS_ENABLED(CONFIG_INET) && level == SOL_IP)
> @@ -5525,6 +5522,15 @@ static int __bpf_setsockopt(struct sock *sk, int level, int optname,
>   	return -EINVAL;
>   }
>   
> +static int __bpf_setsockopt(struct sock *sk, int level, int optname,
> +			    char *optval, int optlen)
> +{
> +	if (!sk_fullsock(sk))
> +		return -EINVAL;
> +
> +	return ___bpf_setsockopt(sk, level, optname, optval, optlen);
> +}
> +
>   static int _bpf_setsockopt(struct sock *sk, int level, int optname,
>   			   char *optval, int optlen)
>   {
> @@ -5675,7 +5681,16 @@ static const struct bpf_func_proto bpf_sock_addr_getsockopt_proto = {
>   BPF_CALL_5(bpf_sock_ops_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
>   	   int, level, int, optname, char *, optval, int, optlen)
>   {
> -	return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen);
> +	struct sock *sk = bpf_sock->sk;
> +
> +	if (optname != SK_BPF_CB_FLAGS) {
> +		if (sk_fullsock(sk))
> +			sock_owned_by_me(sk);
> +		else if (optname != SK_BPF_CB_FLAGS)

This is redundant considering the outer "if" has the same check.

Regardless, "optname != SK_BPF_CB_FLAGS" is not the right check. The new 
callback (e.g. BPF_SOCK_OPS_TS_SCHED_OPT_CB) can still call 
bpf_setsockopt(TCP_*) which will be broken without a lock.

It needs to check for bpf_sock->op. I saw patch 5 has the bpf_sock->op check but 
that check is also incorrect. I will comment in there together.

> +			return -EINVAL;
> +	}
> +
> +	return ___bpf_setsockopt(sk, level, optname, optval, optlen);
>   }
>   
>   static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {